Recently, liquid crystal display devices adopting liquid crystals as a display device have been widely used as a display medium. For example, as shown in FIG. 32, the liquid crystal display device includes an upper glass 101 having a plurality of display-use upper electrodes 103 formed on a surface thereof, a lower glass 102 having a plurality of display-use lower electrodes 104 on a surface thereof. The upper glass 101 and the lower glass 102 are formed so as to face each other in such a manner that respective electrodes cross at a right angle via a seal 105. The liquid crystal display device has a liquid crystal cell having a liquid crystal layer 106 formed by sealing liquid crystals in a space surrounded by the upper and lower glasses 101 and 102 and the seal 105.
In the described arrangement of the liquid crystal display device, the side opposite to a terminal section 104a forming side of the display-use lower electrode 104 is formed inside the seal. For this reason, an interval d2 between a display-use upper electrode 103 forming portion of the upper glass 101 and the display-use lower electrode 104 forming portion of the lower glass 102 differs from an interval di between the upper glass 101 of the display-use upper electrode 103 and the lower glass 102 of the display-use lower electrode 104 in a non-forming area. Namely, there is a difference in thickness in the liquid crystal layer 106 between the electrode forming portion and the electrode non-forming portion of the glasses 101 and 103 of the liquid crystal display device.
Such difference in thickness of the liquid crystal layer 106 causes variations in color of the display screen in an absence of an application voltage to the display-use upper electrode 103 and the display-use lower electrode 104, thereby generating variations in color of the display screen.
Recently, in the liquid crystal display device, especially, in the STN (Super Twisted Nematic) liquid crystal display device, improved display quality is strongly demanded. Especially, in the STN-type color liquid crystal display device, improvements in color variations in a vicinity of the seal in the half tone of the image display is strongly demanded.
Various techniques have been proposed to reduce color variations in a vicinity of the seal in the display area. For example, Japanese Unexamined Patent Publication No. 229234/1987 (Tokukaisho 62-229234) discloses a "liquid crystal display device" which suppresses color variations in the display screen wherein a dummy electrode having a same thickness of a display-use electrode is formed on a substrate on which the display-use electrode is not formed so as to eliminate a difference in thickness of a liquid crystal layer.
As shown in FIG. 33, Japanese Unexamined Utility Model Publication No. 85779/1989 (Jitsukaihei 1-95779) discloses a "liquid crystal display panel wherein a pattern width of the terminal sinuous section 113a of the segment electrode 113 formed on a segment electrode 111 increases as being away from a terminal section (not shown) of a common electrode substrate 112, and a pattern width of the terminal sinuous section 113a is formed between in the pattern of a narrow portion.
Furthermore, as shown in FIG. 34, Japanese Unexamined Patent Publication No. 174414/1991 (Tokukaihei 3-174414) discloses a liquid crystal display device wherein an upper dummy electrode 126 is formed in a portion where a signal electrode 123 is not formed of an upper glass 121 on a seal 125 in a circumferential portion on both sides and a lower dummy electrode 127 is formed in a portion where a scanning electrode 124 is not formed of a lower glass 122.
As shown in FIG. 35, Japanese Unexamined Patent Publication No. 211524/1989 (Tokukaihei 3-211524) discloses a liquid crystal display element wherein an upper electrode substrate 131 wherein a segment electrode 133 is formed on a surface and a lower electrode substrate 132 whereon a common electrode 134 is formed on a surface are formed so as to face the electrode forming surface, and liquid crystals are injected through a sealing opening 137 formed on the sealing opening side 136 of respective substrates 131 and 132.
However, in any of the described Gazettes, members such as the dummy pattern 114, the upper and lower dummy electrodes 126 and 127 and the dummy electrode 138, etc., are formed in a portion which affects the thickness of the liquid crystal layer on the display surface, and this suppresses a difference in thickness of the liquid crystal layer between the display area and the surrounding area of the display, thereby improving color variations in a vicinity of the seal of the display screen.
As described, liquid crystal display devices which adopt the technique disclosed in the above Gazettes have been commercialized to achieve improved color variations in a vicinity of the seal on the display screen. Such liquid crystal display devices, for example, have an arrangement shown in FIG. 36, wherein a signal electrode substrate 141 and a scanning electrode substrate 142 are formed so as to face each other via a seal 145, and a signal electrode sinuous section 143 and a scanning electrode sinuous section 144 of the scanning electrode (not shown) of the signal electrode (not shown) in a vicinity of the seal 145 formed within the display area are divided into a plurality of blocks so as to correspond to the connection terminal with the external circuit.
In the liquid crystal display device having the described arrangement, the electrode sinuous sections 143 and 144 are designed such that the electrodes on the side of the connection terminal for connection with the external circuit have a higher alignment density than that of the electrodes on the side of the display area to achieve improved color variations in a vicinity of the seal 145 of the display area.
However, in the liquid crystal display device shown in FIG. 36, the electrode sinuous sections 143 and 144 are designed so as to have a uniform resistance value of the display-use electrodes (signal electrode and scanning electrode) within a permissible range, and based on the design of the electrodes sinuous sections 143 and 144, the dummy electrode (between electrode dummy electrode and double dummy electrode) are designed. For this reason, a ratio of an area occupied by the display-use electrodes and the dummy electrodes in the seal 145, i.e., the interleaved ratio differs.
Furthermore, as shown in FIG. 15 which explains the present invention, the ratio of an overlapped area S between the display-use electrode and the double dummy electrode which face each other in the seal, i.e., an overlapped ratio also differs in four sides.
As shown in FIG. 10 which explains the present invention, in the case of adopting the color liquid crystal display device adopting the color filter layer 12, as shown in FIG. 11 which explains the present invention, a width x of the signal electrode 3 (one display-use electrode) is about 1/3 of the width (3x+2y) of the scanning electrode 4, i.e., the other display-use electrode. Here, x indicates a line width of the signal electrode 3 and y indicates a line width of the black matrix.
There, in the case of the liquid crystal display device shown in FIG. 36, both the interleaved ratio and the overlapped ratio of the display-use electrode and the dummy electrode in the seal 145 portion greatly differ between the terminal section I constituted by scanning electrode sinuous sections 144 on the scanning electrode side and the terminal section II constituted by the signal electrode sinuous section 143 on the side of the signal electrode.
In the case of the liquid crystal display device shown in FIG. 36, the liquid crystal sealing opening side electrode section 147 is formed on the side of the sealing opening 146 of the liquid crystals. In the liquid crystal sealing opening side electrode section 147, the scanning electrode on the scanning electrode substrate 142 is extended directly to the seal 145 portion, and the double dummy electrode is formed in the seal 145 portion on the signal electrode substrate 141, i.e., the counter substrate. Thus, the interleaved ratio and the overlapped ratio of the display-use electrode and the dummy electrode greatly differs between the terminal section I and the terminal section II.
Generally, the seal includes a glass bead for adjusting the thickness. Such a glass bead is hard and is not deformed with an applied pressure generated when laminating, and thus it is distinguishable from a parasitic spacer for use in determining the thickness of the liquid crystal layer in the display area. Therefore, the thickness of the liquid crystal layer in a vicinity of the seal can be adjusted by adjusting the diameter of the glass bead contained in the seal.
Specifically, as shown in FIG. 37, the glass bead 156 of the within seal spacer contained in the seal 155 sandwiched between the display-use substrates 151 and 152 is classified into three groups: (i) a glass bead 156a sandwiched between the display-use electrode 153 and the dummy electrode 154, a glass bead 156b sandwiched in a portion where only the display-use electrode 153 is formed in-between, and a glass bead 156c in a portion where either of the electrodes 153 and 154 is formed in-between. Although not shown in FIG. 37, the glass beads may be formed so as to have only the dummy electrode 154 in-between.
In view of all sides, as the glass bead 156a sandwiched between the display-use electrode 153 and the dummy electrode 154 serves as a support, the thickness of the seal 155 is determined mainly by the diameter of the glass bead 156a. However, when locally seen, in the region where the glass beads 156a, 156b and 156c exists, the respective thickness of the seal 155 are as indicated by d3, d2 and d1 (d3 &gt;d2&gt;d1). Namely, the glass beads 156b and 156c are in a floated state.
Therefore, as in the conventional liquid crystal display device shown in FIG. 32, the difference in the overlapped ratio of the display-use electrode and the dummy electrode which face each other in respective sides of the seal 145 causes a difference in the number of glass beads having the different diameters in the seal 145 in the sides, thereby creating a difference in thickness of the seal 145 in four sides. Therefore, variations in thickness of the liquid crystal layer occurs in the display area in a vicinity of the seal 145. As a result, color variations occur in the four sides, thereby reducing a display quality.
As described, the difference in thickness in four sides of the seal 145 makes it difficult to adjust the thickness in a vicinity of the display area central portion and the vicinity of the seal 145. Namely, only by adjusting the diameter of the glass bead contained in the seal 145, a uniform thickness of the seal 145 in the four sides cannot be achieved. As a result, a difference in brightness occurs between the central portion of the display area and the portion in a vicinity of the four sides of the seal 145, thereby reducing a display quality.